Casting magnesium and alloy thereof



March 5, 1929. J. A. GANN ET AL 1,704,384

CASTING MAGNESIUM AND ALLOY THEREOF Filed Jan. 14, 1926 I Nl 'ENTOR Patented Mar. 5, 19253.l

JOHN A. GANN AND' JOHN E. HOY, OF MIDLAND, MICHIGAN, ASSIQNOBS T0 TH PATENT oFFlcE.

CHEMICAL COMPANY, OF MIDLAND, MICHIGAN, A CORPORATIN 0F MICHIG CASTING MAGNESIUM AND ALLOY Trimmer.

Application led January 14,` 1926. Serial No. 81,304.

While the present improvements relate. more particularly to the casting of magnesium and so-called light metal alloys 1n which magnesium is the predominant constituent, it will be understood that the improved method and apparatus involved are equally adaptable for the casting of any similar prevent the cast article from bein'g prop-l erly finished when removed from the mold, a certain loss of metal, due to oxidation, is 1n# evitable, and of course the cleaner the casting, the more easily may the finishing operation be carried out;

It has heretofore been proposed to overcome these difficulties specifically in casting magnesium and alloys containing the same by dusting the mold prior to casting the metal with sulphur or equivalent material capable of giving off in contact with the 'molten' metal a vapor which is more easily oxidizable than magnesium. This procedure, however, has the objection that it is obviously difHcult correctly to gauge the amount of sulphur or equivalent material thus used, and particularly if an excess' is applied to the surface either of the mold proper or the core, so much vapor may be generated that some of 1t becomes entrapped during the period that the metal 1s solidifying, the result being blow-holes or surface shrinks in the casting. Furthermore, the sulphur or equivalent material has to be applied or dusted onto the mold each time a fresh casting is poured and -1n any case the method in question is obviouslylnot applicable wherea metal mold is employed, because of the non-porous character `of the latter. Y.

By the present improved construction of mold we make it possible to supply to the mold cavity an inert or reducing gas, specically sulphur dioxide, vin an amountl suf- .the offset 4 in the mold w ficient to displace the air normally filling a continuous supply of such inert or reducing gas while a succession of castingsis being poured in the same mold.

To the accomplishment of the foregoing and related ends, the invention, then, consists of the steps and means hereinafter fully describedand particularly pointed out in the claims, the annexed drawing and the following description setting forth in detail certain means and one mode of carryin out the invention,` such disclosed means an mode illustrating, however, -but one of various ways in which the principle ofthe invention may be used.

In said annexed draw-ing:-

The single figure there appearing is a central vertical section through a mold con. structed and arranged to carry out our improved method.

The mold thus illustrated is specifically designed for casting a iston for an internal combustion engine or ike hollow article of general cylindrical form. The mold part 1 will preferably be of metal, e. g. cast iron, as is commonly used in foundries at vthe present time for casting light metal pistons, but such mold may be made of sand, if desof sired. Such permanent mold has a cavity 2 adapted to volatilize by the heat of the mold and give ofl' an inert gas that is heavier than air or that may be ignitedand give off such a gas. The core 6, which may be either of sand or of collapsible metal parts, is of course separable from themold l and is formed with an enlargement 7 at its upper end ada ted to fit the enlarged portion 3 of the mol cavity, the shoulder 8 between such enlargement and the core plroper resting on en the parts areproperly assembled. y

'When thus 5 in place, such shoulder will seal off .the chamber 5 save for a slit-like vent opening or openings 41() which are so narrow that molten metal will solidify bein which the casting is to be formed.

In operat-ion, atte;` the mold part 1 has,

beenpreliminarily warmed up, the gas producing material hereinbefore referred to is placed in the chamber 5,'or a small quantity of sulphur is-strewn around in such chamber and ignited. Then as the core 6A is put in place, the gas generated from such material is trapped and forced out through the vent l() into the cavity 2, expelling the air through the gate opening 12 and spnue 11. When this has been accomplished, the moltenl metal is then poured into the mold in the usual manner. The material 13 in the chamber can be replenished from time to time in the case where a permanent mold part 1 is used. As an example of a material that will generate a suitable inert gas as a result of the heat derived from the mold, para dichlor-benzol may be named, although this material has the disadvantage that the gases generated are more obnoxious than the sulphur dioxide formed by burning sulphur, as"also naphthalene, carbon tetrachloride, and fuel oil. In no case, however, does the material used thus to generate the neutral or reducing gas 'come into direct contact with the surfaces There is, accordingly, no danver of-an excessive amount oflsuch gas being generated with resultant formation .of blow-holes or surface shrinks.

Other modes of applying the principle vo our invention may be employed instead of the one explained, change being made as regards the means and the steps herein dis- I dizable metal, the combination .of separable moldparts', one of said parts having'a chamber normally open to the atmosphere wherein y a non-oxidizing as may be generated, and

`the other partfbem-g adapted, when in position for eastingrto' seal oil?` such chamber save for a vent into the-. i`no1d cavity.

2. In apparatus for casting a readilymxidizable metal, the combination of a separable mold and core, said mold having a chamber substantially encircling the `cavity vtherein and normally open to' the atmosphere and said core having a portion to seal olf such chamber save for a communicating vent.

'3. In apparatus for casting a readily oxidizablc metal, the combination of a separable mold and core,said mold having a chamber substantially encircling the cavity therein and normally open to the atmospbereand said'core .having a portion arranged, when said core is in position for cast-ing, to seal -otf such chamber save for a slit-like vent, the latter being so narrow that molten metal will solidify before lowing therethrough into such chamber.

4. Inapparatus for casting pistons and other .articles of general cylindrical shape from a readily oxidizable metal, the combination of a separable mold and core, said mold having a cavity conforming to the exterior shape of the article to be cast and an.

enlargedspace continuous with the upper end of such cavity, whereby a lateral offset is provided substantially encircling such cavity, with a depression in such offset adapted to receive and contain a gas-generating material, and said core having a lat-eral shoulder fitted to such enlarged space in said mold to seal oft' such depression@ save for, a slit-likevent opening into .the mold cavity.

5. In apparatus. for casting -pistons and other articles of general cylindrical shape from a readily oxidizable metal, theconibination of a separable mold and core, said mold having a cavity conforming to the ex terior shape of the article to be cast and an enlarged space continuous with the upper end of such cavity, whereby a lateral o'set is. provided substantially encircling such cavity, with a depression' in such offset adapted to receive and contain a gas-generat-l ing material, and said core having a lateral shoulder Vfitted to such enlarged space in said-mold to seal Voil` such depression save' foi` a slit-like vent opening into the mold cavit so narrow that molten metal will solidly before flowing therethrough.

Signed by us this 7th day of J anuary, 1926-.

*JOHN AQ GANN. JOHN E. Hor. 

